The nighthawks follow paths that lead them in vast circles over miles of fields and thickets.

Some birds follow the river or coastline, others follow the ridge. All follow the stars and their own magnetic senses. Young birds follow their parents and make maps of the routes and places where they have been led. This is the way they come home, both to where they were born, and to where there is warmth and sustenance.

September is when tropical songbirds leave the land of nests and follow the slowly tilting sun. On their way they stop to rest and feed. They can end up anywhere for a day or two, even many days if the weather is wet or winds adverse. If you stop to look, you might find these travelers not far from your own home, or in your own yard.

One of the first migrants of fall is the nighthawk, a bird that once nested on city buildings in our region. I can remember many years ago, waiting at dusk for the first nighthawk to circle the rooftops of Westfield, its nasal calls buzzing round my ears like the twilight itself.

Nighthawks now only nest farther north, in upland fields, rocky pastures or burned over forests, all places growing scarcer. There are still enough to make a parade southward through our late summer evening skies, after they spend an hour or more to feed.

When the sun is still sending light over the western hills, the nighthawks follow paths that lead them in vast circles over miles of fields and thickets. They dive and dart after flying insects, and sometimes stop to form a whirlpool of birds when they encounter a recent hatch of flying ants that has risen to swarm.

During the first evening watch from my second story deck a single bird flew over, one that I hoped was a lonely signal of more to come. Other birds that feed in flight were active on this mild evening, a handful of swallows and a single chimney swift. The nighthawk dwarfs these puny minions in size, but it does not outfly them.

Three days later, 20 nighthawks flew south. They flew overhead one or two at a time, their long wings arched above their bodies when the bird sailed, but rowing deeply when in powered flight. There were long waits between each bird and each pair of birds.

That evening, another migrant tarried to entertain me during the long periods of empty sky. An olive-sided flycatcher perched in the dead twigs that rose above the flowing leaves of the ancient willow tree. It sallied out every few minutes to catch a wayward insect.

The next evening, the wait was very long, until a flock of forty nighthawks flew over in one quick flurry, heading north, perhaps in search of better foraging. The night was warm and when I rose before dawn, a whip-poor-will called from the woods behind the house. This close cousin of the nighthawk would probably leave soon, not to be heard again until next April.

Two days later the evening watch brought a loose parade of nighthawks overhead and moving south, a total of 74 in an hour and a half. Many more had already been counted at other watches over the previous week, so it was likely my last look at these birds: or was it?

It was the second day of September, and the evening was cool and cloudy. Four days of rain had intervened since the last evening flight. I came to my perch late, and found the nighthawks parading past as if it was their last chance to fly.

They tarried only for an occasional twist to capture nearby prey in their enormous mouths. They were not hard to count, and the total rose steadily higher and higher. Sometimes a dozen or more would come in a spurt, and sometimes a minute or two would pass with empty skies.

That north-south running ridge was likely a guide, one that the nighthawks knew and followed, knowing there were other paths farther along that would lead them out of New England. The count of birds passing that night was just over 500, my best flight of nighthawks in many years.

Seth Kellogg can be contacted at skhawk@comcast.netThe Allen Bird Club website can be found at massbird.org/allen